delegate_to

You can run a task on a specific host using delegate_to.

- name: Do something on the first host
  ansible.builtin.command:
    cmd: ls
  delegate_to: ""

The above example will run the ls command on the first host in the all group.

You may want to use this pattern to run something on another node. An example can be to register a system to a CMDB:

- name: Install stuff on a node
  ansible.builtin.package:
    name: "stuff"

- name: Register this node to the CMDB
  ansible.builtin.uri:
    url: "https://cmdb.example.com/register"
    method: POST
    body: ""
  delegate_to: localhost

Assignment

Create a playbook that stores the hostname of the current node in a file on localhost; /tmp/hosts.txt

Solution

A hacky attempt that works.